Stretch wrapping machine

ABSTRACT

Provided is a stretch wrapping machine that can stably convey film even in a case where, for the purpose of wrapping, a holding component that holds the film is provided separately from belts for conveyance. The stretch wrapping machine is equipped with conveyance devices ( 22 ) having belt conveyance units and belt pressing mechanisms, a clamp device ( 23 ), a wrapping station, and a control device ( 9 ). At the wrapping station, product is pushed against film held by the clamp device ( 23 ), and the product is wrapped by the film. The belt conveyance units have upper belts and lower belts that sandwich end portions of the film. Pressing members ( 221   e ) of the belt pressing mechanisms apply force to the upper belts so that the force with which the upper belts and the lower belts sandwich the film increases. Additionally, the control device ( 9 ) controls the belt pressing mechanisms so that during conveyance of the film the force resulting from the pressing members ( 221   e ) acts on the upper belts and so that after conveyance of the film the force resulting from the pressing members ( 221   e ) that had acted on the upper belts is cancelled.

TECHNICAL FIELD

The present invention relates to a stretch wrapping machine.

BACKGROUND ART

Stretch wrapping machines are known as machines that wrap a wrappingitem such as perishable food. As described in patent document 1 (JP-ANo. 2006-327670) for example, a stretch wrapping machine pushes up thewrapping item against stretched film and in that state tucks the filmunder the wrapping item. In the stretch wrapping machine disclosed inthis document, the film paid out from a film roll is conveyed by pairsof upper and lower conveyor belts.

DISCLOSURE OF INVENTION Technical Problem

In the stretch wrapping machine described above, a clamp device isprovided separately from the pairs of upper and lower conveyor beltsthat sandwich the film during conveyance, and the clamp device (aholding component) clamps both side end portions of the film after thefilm is conveyed by the conveyor belts. Then, the wrapping item ispushed up against the film held by clamp device, and wrapping isstarted.

Additionally, the clamp device is disposed so as to hold the film on theinner side of the conveyor belts disposed on both sides, and does notapply force to the film when the film is conveyed by the conveyor belts.

However, in a stretch wrapping machine that employs a structure wherethe clamp device is away from the conveyor belts in this way, there arecases where part of the film—for example, the leading section in theconveyance direction—conveyed while being held by the conveyor beltscomes away from the conveyor belts and sags. In this case, the filmbecomes slack prior to the wrapping, resulting in the visualattractiveness of the wrapping becoming poor and hindrances occurring inthe conveyance of the film.

It is a problem of the present invention to provide a stretch wrappingmachine that can stably convey film even in a case where, for thepurpose of wrapping, a holding component that holds the film is providedseparately from belts for conveyance.

Solution to Problem

A stretch wrapping machine pertaining to a first aspect of the presentinvention comprises a conveyance component, a holding component, awrapping component, and a control component. The conveyance componentconveys film pulled out from a film roll. The holding component holdsthe film conveyed by the conveyance component. The wrapping componentpushes a wrapping item against the film held by the holding componentand uses the film to wrap the wrapping item. The control componentcontrols the operations of the conveyance component, the holdingcomponent, and the wrapping component. Furthermore, the conveyancecomponent has a first conveyance unit and a force applying component.The first conveyance unit includes a first belt and a second belt thatsandwich an end portion of the film. The force applying componentapplies force to the first belt so that the force with which the firstbelt and the second belt sandwich the film increases. Additionally, thecontrol component controls the force applying component so that duringthe conveyance of the film by the conveyance component the forceresulting from the force applying component acts on the first belt andso that after the conveyance of the film by the conveyance component theforce resulting from the force applying component that had acted on thefirst belt is cancelled.

In this stretch wrapping machine, during the conveyance of the film theforce from the force applying component acts on one (the first belt) ofthe first belt and the second belt that sandwich the end portion of thefilm, so the force with which both belts sandwich the film becomesstronger. Because of this, the conveyance of the film becomes carriedout stably. After the conveyance of the film the force that had acted onthe first belt from the force applying component is cancelled, so theconveyed film is no longer excessively restrained by both belts, and thewrapping of the wrapping item by the wrapping component with the filmheld by the holding component is also carried out excellently.

A stretch wrapping machine pertaining to a second aspect of the presentinvention is the stretch wrapping machine pertaining to the firstaspect, wherein after the conveyance of the film by the conveyancecomponent the control component has the holding component hold the filmand causes the wrapping by the wrapping component to be carried out in astate in which the force resulting from the force applying componentthat had acted on the first belt is cancelled.

In this stretch wrapping machine, the force that had acted on the firstbelt from the force applying component is cancelled prior to thewrapping, so the wrapping can be started in a state in which the film isnot being excessively restrained by both belts. Because of this, thewrapping is stable.

A stretch wrapping machine pertaining to a third aspect of the presentinvention is the stretch wrapping machine pertaining to the first aspector the second aspect, wherein the holding component has a first holdingmember in which a first holding surface is formed and a second holdingmember in which a second holding surface that opposes the first holdingsurface is formed. Additionally, the first holding member and the secondholding member hold the film by sandwiching a section of the film otherthan the section of the film positioned between the first belt and thesecond belt.

In this stretch wrapping machine, the section of the film sandwiched byboth holding members of the holding component is not the section of thefilm between the first belt and the second belt but is located in aposition away from that section. For this reason, the position of thesection of the film held by the holding component can be set in aposition suitable for the wrapping.

A stretch wrapping machine pertaining to a fourth aspect of the presentinvention is the stretch wrapping machine pertaining to the thirdaspect, wherein the force applying component has a pressing member inwhich a pressing surface that presses the first belt is formed and adrive component that moves the pressing member. Additionally, the areaof the pressing surface of the pressing member is smaller than that ofthe first holding surface of the first holding member.

In this stretch wrapping machine, the area of the pressing surface ofthe pressing member of the force applying component is small, and thearea of the first holding surface of the first holding member of theholding component is larger than that. Because of this, the film can bestrongly held by the holding component when pushing the wrapping itemagainst the film. Furthermore, during the conveyance of the film,frictional resistance between the pressing surface of the pressingmember and the first belt can be kept down.

A stretch wrapping machine pertaining to a fifth aspect of the presentinvention is the stretch wrapping machine pertaining to any of the firstaspect to the fourth aspect, wherein the first conveyance unit uses thefirst belt and the second belt to sandwich the end portion which is oneend portion of the film and convey the film. The conveyance componentfurther has a second conveyance unit. The second conveyance unit uses athird belt and a fourth belt to sandwich another end portion of the filmand convey the film. Furthermore, the stretch wrapping machinepertaining to the fifth aspect further comprises a first unit movingcomponent and a second unit moving component. The first unit movingcomponent causes the first conveyance unit to move in a film widthdirection intersecting a conveyance direction of the film. The secondunit moving component causes the second conveyance unit to move in thefilm width direction. Additionally, in accordance with the widthdimension of the film the control component changes a first distance bycontrolling the first unit moving component and changes a seconddistance by controlling the second unit moving component. The firstdistance is a distance from one end edge of the film in the one endportion of the film sandwiched by the first belt and the second belt ofthe first conveyance unit. The second distance is a distance fromanother end edge of the film in the other end portion of the filmsandwiched by the third belt and the fourth belt of the secondconveyance unit.

This stretch wrapping machine employs a configuration where the firstconveyance unit that uses the first belt and the second belt to sandwichthe one end portion of the film and the second conveyance unit that usesthe third belt and the fourth belt to sandwich the other end portion ofthe film move together in the film width direction. Additionally, bymoving the conveyance units in accordance with the width dimension ofthe film, the first distance and the second distance are changed inaccordance with the width dimension of the film. Because of this, thedistances from the film end edges in the sections of the film sandwichedby both belts of each conveyance unit can be set to appropriatedistances in accordance with the film width, and slackness in the filmduring film conveyance is reduced or the film is kept from coming outfrom between both belts of each conveyance unit.

A stretch wrapping machine pertaining to a sixth aspect of the presentinvention is the stretch wrapping machine pertaining to the fifthaspect, wherein the control component increases the first distance andincreases the second distance when the width dimension of the filmincreases.

In this stretch wrapping machine, the first distance and the seconddistance increase when the width dimension of the film increases, soeach conveyance unit conveys the film while sandwiching, with bothbelts, sections of the film positioned more inward in the film widthdirection when the width dimension of the film is large than when it issmall. Because of this, there is less sagging in the film widthdirection central section of the film, and the conveyance of the film isstable.

Advantageous Effects of Invention

According to the stretch wrapping machine pertaining to the presentinvention, the film sandwiching force resulting from both belts duringthe film conveyance becomes stronger so that the film conveyance becomesstable, and after the conveyance of the film there is no longerexcessive restraining of the film by both belts so that the wrapping iscarried out satisfactorily.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an external perspective view of a stretch wrapping machinepertaining to an embodiment of the present invention.

FIG. 2 is a front general view of the interior of the stretch wrappingmachine.

FIG. 3 is a perspective view seen from arrows of FIG. 2.

FIG. 4 is a front general view of the interior of the stretch wrappingmachine.

FIG. 5 is a general plan view of a film insertion plate unit.

FIG. 6 is a plan general view of the interior of the stretch wrappingmachine.

FIG. 7 is a correlation diagram of a first unit, a second unit, and twounit moving devices.

FIG. 8 is a perspective view of the second unit excluding belts.

FIG. 9 is a side general view of the second unit.

FIG. 10 is a side general view of the second unit in a state in whichforce is applied from a pressing member to an upper belt.

FIG. 11 is a plan arrangement diagram of clamp members and pressingmembers.

FIG. 12 is a drawing showing some control targets of a control device.

FIG. 13 is a drawing for describing the operation of the stretchwrapping machine.

FIG. 14 is a drawing for describing the operation of the stretchwrapping machine.

FIG. 15 is a drawing for describing the operation of the stretchwrapping machine.

FIG. 16 is a drawing for describing the operation of the stretchwrapping machine.

FIG. 17 is a drawing for describing the operation of the stretchwrapping machine.

FIG. 18 is a drawing showing solenoid control during film conveyance.

FIG. 19 is a drawing showing control of forward and backward movement,corresponding to film width, of each unit of a film conveyance andholding mechanism.

FIG. 20 is a drawing showing proper first distances and second distancescorresponding to the width dimension of the film.

FIG. 21 is a front general view of the interior of the stretch wrappingmachine pertaining to example modification C.

DESCRIPTION OF EMBODIMENT

A stretch wrapping machine 1 pertaining to an embodiment of the presentinvention will be described below with reference to the drawings.

(1) Configuration of Stretch Wrapping Machine 1

FIG. 1 is an external perspective view of the stretch wrapping machine1. In the following description, expressions indicating directions—suchas front/rear/left/right, upper/lower, front surface, and backsurface—will be used, and unless otherwise specified these will beunderstood to mean the directions shown in the lower right of FIG. 1.

First, a general overview of the stretch wrapping machine 1 will bedescribed. The stretch wrapping machine 1 is a machine that pushes, frombelow, a tray T containing product G such as perishable food(corresponding to a wrapping item) against tensioned held film F (seeFIG. 14, etc.) and tucks the peripheral edge portions of the film Funder the tray T to thereby wrap the tray T in the film. It will benoted that a method of use where the product G is wrapped without beingcontained in the tray T is also possible.

The configuration of the stretch wrapping machine 1 will be describedbelow using FIG. 1 to FIG. 7.

The stretch wrapping machine 1 is equipped with a loading mechanism 2, awrapping station 3, a roll support mechanism 4, a film feed mechanism 5,a film conveyance and holding mechanism 6, a sealing mechanism 8, and adischarge table 11. The wrapping station 3 has a lifter mechanism 30 anda tucking mechanism 7 as a wrapping component.

(1-1) Loading Mechanism 2

The loading mechanism 2 is provided on the front surface side of a body1 a of the stretch wrapping machine 1 and functions as a loadingcomponent by which the tray T containing the product G is loaded intothe body 1 a. The loading mechanism 2 has a weigh scale that weighs theproduct G contained in the tray T, a weigh pan placed on the weighscale, and plural infeed conveyor belts provided between a pair ofrollers. Projections for conveyance are provided on the infeed conveyorbelts. When the tray T containing the product G is placed on the weighpan as shown in FIG. 3, the product G is weighed by the weigh scale andthereafter the tray T is pushed from the front surface side by theprojections secured to the infeed conveyor belts and delivered ontosupport members 33 of the lifter mechanism 30 of the wrapping station 3.

(1-2) Wrapping Station 3

The wrapping station 3 is a wrapping space formed in the body 1 a. Thewrapping station 3 has the role of a wrapping component that administersa series of wrapping operations on the tray T including the product Gthat has been weighed. The wrapping station 3 has the lifter mechanism30 and the tucking mechanism 7 as a wrapping component. When the film F(stretch film) is stretched by the film conveyance and holding mechanism6, the lifter mechanism 30 pushes the tray T containing the product Gagainst the stretched film F (see FIG. 15). Then, the tucking mechanism7 tucks the peripheral portions of the film F under the tray T havingthe film F pressed against it, whereby the tray T and the product Gbecome covered by the film F.

The lifter mechanism 30 is provided in the lower portion of the wrappingstation 3. The lifter mechanism 30 functions as a raising and loweringmechanism that holds the bottom surface of the tray T and raises up andlowers down the tray T and the product G As shown in FIG. 3, the liftermechanism 30 has a support base 31, plural support bars 32 secured onthe support base 31, and support members 33 supported in such a way thatthey may freely turn on the upper end portions of the support bars 32and which receive the bottom surface of the tray T. Furthermore, anelectrically powered ball screw mechanism 34 that moves the support base31 up and down is disposed in the lower portion of the lifter mechanism30.

It will be noted that each support bar 32 has in its central portion ahinge that bends forward/backward and rightward/leftward, and the hingeis configured to temporarily fall over when right and left tuckingplates 76 and 77 (see FIG. 2 and FIG. 3) and a rear tucking plate 78 ofthe tucking mechanism 7 come under the tray T.

As shown in FIG. 2 and FIG. 3, the tucking mechanism 7 has right andleft tucking plates 76 and 77, a rear tucking plate 78, and a fronttucking rod 79. The right and left tucking plates 76 and 77 tuck bothfilm conveyance direction end portions of the film F to the bottomsurface side of the tray T. The rear tucking plate 78 tucks the sideportion of the film F on a second unit 62 side to the bottom surfaceside of the tray T. The right and left tucking plates 76 and 77 and therear tucking plate 78 can be moved horizontally by motors and timingbelts not shown in the drawings. The front tucking rod 79 is disposed insuch a way that, when the tray T is discharged, the side portion of thefilm F on a first unit 61 side becomes tucked to the bottom surface sideof the tray T. The discharging of the tray T is carried out by adischarge pusher 75 pushing the tray T out toward the sealing mechanism8 (the front surface side).

Furthermore, a hold-down mechanism 81 is disposed in the upper portionof the wrapping station 3. The hold-down mechanism 81 keeps the tray Tand the product G from losing their posture and falling over when theproduct G and the tray T resting on the lifter mechanism 30 are pushedup and stop (see FIG. 15).

(1-3) Roll Support Mechanism 4

The roll support mechanism 4 is a mechanism that supports film rolls R,and as shown in FIG. 2 is disposed in the left side portion of the body1 a. The roll support mechanism 4 is mainly configured from two rollbars. The roll bars are inserted through the film rolls R and hold thefilm rolls R using holders or the like. The roll bars are supported insuch a way that they may freely rotate in the body 1 a. A pulley 4 b issecured to one end of each roll bar, and a belt 4 c is entrained abouteach pulley 4 b. The two roll bars are disposed out of alignment witheach other in the up/down and right/left directions.

The belts 4 c are driven by one film roll drive motor 4 d. The film rolldrive motor 4 d is capable of forward and reverse rotation; when thefilm roll drive motor 4 d forwardly rotates, the film roll drive motor 4d drives in such a way that the film roll R having one roll bar insertedthrough it is rotated, and when the film roll drive motor 4 d reverselyrotates, the film roll drive motor 4 d drives in such a way that thefilm roll R having the other roll bar inserted through it is rotated.One-way clutches 4 e are provided between the belt 4 c and the film rolldrive motor 4 d.

(1-4) Film Feed Mechanism 5

The film feed mechanism 5 is a mechanism for feeding to the filmconveyance and holding mechanism 6 the film F that has been pulled outfrom the film rolls R. As shown in FIG. 2 and FIG. 5, the film feedmechanism 5 is mainly configured from a film insertion plate unit 51 forholding the film F and a film insertion plate drive motor (not shown inthe drawings) that causes the film insertion plate unit 51 to swingusing a predetermined shaft as a fulcrum.

The film insertion plate unit 51 has a first film insertion plate 51 amainly configured from two plate members 57 a and 58 a and a second filminsertion plate 51 b mainly configured from two plate members 57 b and58 b.

The film insertion plate unit 51 is disposed above the film rolls R andextends along the longitudinal direction of the film rolls R. It will benoted that the longitudinal direction length of the film insertion plateunit 51 is longer than the longitudinal direction length of the filmrolls R.

Cutouts 53 a to 53 h are formed in each of the two plate members 57 aand 58 a. Although FIG. 5 shows only the plate members 57 a and 58 a,the two plate members 57 b and 58 b have the same configuration. Below,the plate members 57 a and 58 a will be taken as an example anddescribed. The distances between the cutouts 53 a and the cutouts 53 bto 53 h are distances corresponding to several types of film F havingdifferent film widths. For example, the distance between the outer sideof the cutouts 53 a and the outer side of the cutouts 53 h generallycoincides with the film width of the film F having the largest filmwidth.

It will be noted that the width dimension of the cutouts 53 a is largerthan the width dimension of the other cutouts 53 b to 53 h, but thiswill be described in detail later.

The two plate members 57 a and 58 a are coupled to each other at one endby a hinge not shown in the drawings, so that the two plate members 57 aand 58 a can open and close. Because of this, the operator can easilyinsert the film F between the plate member 57 a and the plate member 58a. As shown in FIG. 5, the plate member 57 a and the plate member 58 ahave substantially the same shape.

The film insertion plate drive motor causes the film insertion plateunit 51 to swing in a predetermined range using the hinge section as ashaft. Because of the film insertion plate drive motor, the filminsertion plate unit 51 can take, for example, a first position (theposition indicated by the long dashed short dashed lines in FIG. 2) anda second position (the position indicated by the long dasheddouble-short dashed lines in FIG. 4) positioned below the firstposition. Specifically, the first position is a position in which thelongitudinal direction of the second film insertion plate 51 b extendsin a substantially horizontal direction (a position in which the secondfilm insertion plate 51 b is substantially parallel to later-describedbelt conveyance units 220). The second position is a position in whichthe longitudinal direction of the first film insertion plate 51 aextends in a substantially horizontal direction (a position in which thefirst film insertion plate 51 a is substantially parallel to the beltconveyance units 220).

It will be noted that the film insertion plate unit 51 is positioned ineither the first position or the second position while the stretchwrapping machine 1 is operating. The operator selects the position ofthe film insertion plate unit 51 by deciding which of the two disposedfilm rolls R to use.

Furthermore, the film insertion plate drive motor causes the filminsertion plate unit 51 to move horizontally toward the film conveyanceand holding mechanism 6. This allows the film feed mechanism 5 to handover the film F to the film conveyance and holding mechanism 6.

(1-5) Film Conveyance and Holding Mechanism 6

The film conveyance and holding mechanism 6 receives the film F fedthereto from the film feed mechanism 5 and conveys the film F to thecentral section of the wrapping station 3. Furthermore, after conveyingthe film F to the wrapping station 3, the film conveyance and holdingmechanism 6 tensions and holds the film F in preparation for thewrapping operation by carrying out a stretching operation.

The film conveyance and holding mechanism 6 mainly has a first unit 61,a second unit 62, a first unit moving device 63, a second unit movingdevice 64, and a conveyance drive unit 65.

As shown in FIG. 6, the first unit 61 is disposed in the frontsurface-side section of the body 1 a. The second unit 62 is disposed inthe back surface-side section of the body 1 a.

The first unit 61 and the second unit 62 sandwich, using pairs of upperand lower belts (upper belts 221 and lower belts 222), both widthdirection side portions of the film F (i.e., the front surface-sidesection and the back surface-side section of the film F) held by thefilm insertion plate unit 51 and convey, with the conveyance drive unit65, the film F in the direction of arrow A1 (see FIG. 2).

Furthermore, the first unit 61 moves in the width direction of the filmF by activation of the first unit moving device 63, and the second unit62 moves in the width direction of the film F by activation of thesecond unit moving device 64. Both the first unit 61 and the second unit62 are supported in such a way that they may freely move in the widthdirection of the film F along slide shafts 66 and 67 extending along thewidth direction of the film F.

As shown in FIG. 7, the unit moving devices 63 and 64 have drive motors63 a and 64 a and belts 63 b and 64 b that move in the width directionof the film F by activation of the drive motors 63 a and 64 a.Additionally, the units 61 and 62 individually move in the widthdirection of the film F by activation of the belts 63 b and 64 b.

The detailed configuration of the first unit 61 and the second unit 62will be described below. It will be noted that because the first unit 61and the second unit 62 have generally the same configuration, mainly thesecond unit 62 will be taken as an example and described below.

FIG. 8 is a perspective view of the second unit 62. FIG. 9 is a frontview of the second unit, and shows the upper belt 221 and the lower belt222 not shown in FIG. 8. FIG. 10 is a front view of the second unit, andshows a state in which the lower surface section of the upper belt 221is pressed down to the lower belt 222 by a pressing member 221 a of alater-described belt pressing mechanism (force applying device) 90. FIG.11 is a general plan view of the first unit 61 and the second unit 62,and shows the planar arrangement of clamp members 250 to 252 of a clampdevice 23 functioning as a holding component for holding the film Fafter conveyance, pressing members 221 e of belt pressing mechanisms 90,the upper belts 221, and the lower belts 222.

As shown in FIG. 8, the second unit 62 mainly comprises a frame 21, aconveyance device 22, and a clamp device 23.

The frame 21 configures a frame of the first unit 61 and supportspulleys that support the upper belt 221 and the lower belt 222, areceiving unit 230, solenoids 62 b to 62 d (see FIG. 12) that drive theclamp members 250 to 252, a solenoid 62 e and a non-illustrated springmember that drive a pressing member 221 e, the clamp members 250 to 252,and a support shaft 62 f of the pressing member 221 e.

(1-5-1) Conveyance Device 22

The conveyance device 22 mainly has a belt conveyance unit 220, areceiving unit 230, and a belt pressing mechanism 90.

(1-5-1-1) Belt Conveyance Unit 220

The belt conveyance unit 220 contacts both the upper and lower surfacesof the film F and conveys the film F to the wrapping station 3, and isconfigured from the upper belt 221 and the lower belt 222 (see FIG. 9).The upper belt 221 contacts the upper surface—which is one surface—ofthe film F and is positioned above the lower belt 222. As shown in FIG.9, the upper belt 221 is entrained about four pulleys 221 a, 221 b, 221c, and 221 d.

The lower belt 222 contacts the lower surface—which is the othersurface—of the film F. As shown in FIG. 9, the lower belt 222 isentrained about four pulleys 222 a, 222 b, 222 c, and 222 d.Additionally, when a drive motor 65 a (see FIG. 12) is driven by acontrol device 9, driving force resulting from the drive motor 65 a istransmitted via a belt and the like to one of the four pulleys 222 a,222 b, 222 c, and 222 d. More specifically, the lower belts 222 of bothunits 61 and 62 have a setup where they move synchronously owing to thedriving force resulting from the drive motor 65 a of the conveyancedrive unit 65. It will be noted that the upper belt 221 located abovethe lower belt 222 moves following the movement of the lower belt 222via a gear (not shown in the drawings).

(1-5-1-2) Receiving Unit 230

The receiving unit 230 is disposed in the left side section of thesecond unit 62, that is, in the neighbourhood of the film feed mechanism5, and receives the film F fed thereto from the film feed mechanism 5.As shown in FIG. 8, the receiving unit 230 is configured from a frame,the pulley 221 a attached to the frame, and a shaft member 231 a servingas a spindle on which the receiving unit 230 swings. The pulley 221 a issupported by the shaft member 231 b, whereby the pulley 221 a is securedto the frame. The upper belt 221 is, as described above, entrained aboutthe pulley 221 a. That is, the upper belt 221 is integrated with thereceiving unit 230 via the pulley 221 a. Thus, the upper belt 221 alsohas the functions of a gripping component that grips the film F, anintroducing component that introduces the gripped film F to the filmconveyance and holding mechanism 6, and a conveyance component forconveying the film F to the wrapping station 3.

The receiving unit 230 of the second unit 62 swings using the shaftmember 231 as a spindle so to take a first posture (see FIG. 8) and asecond posture (see FIG. 9) by activation/non-activation of atwenty-first solenoid 62 a (an eleventh solenoid 61 a in the receivingunit 230 of the first unit 61). The first posture is a posture in whichthe longitudinal direction (i.e., the right-left direction) of thereceiving unit 230 is a substantially horizontal direction. The secondposture is a posture in which the longitudinal direction of thereceiving unit 230 is inclined upward relative to the horizontal plane.

When the twenty-first solenoid 62 a is activated, the distal end portionof the receiving unit 230 is pushed down using the shaft member 231 a asa spindle and the receiving unit 230 moves to a predetermined position(i.e., the receiving unit 230 takes the first posture). Because of this,the gripping component of the upper belt 221 entrained about the pulley221 a comes into contact with the film. When the activation of thetwenty-first solenoid 62 a is cancelled, the distal end portion of thereceiving unit 230 is pushed up using the shaft member 231 a as aspindle and the receiving unit 230 returns to a predetermined position(the second posture). Because of this, the gripping component of theupper belt 221 goes out of contact with the film.

Consequently, by activating the eleventh and twenty-first solenoids 61 aand 62 a, the gripping components of the upper belts 221 of the units 61and 62 come into contact with the film F, so the film F fed from thefilm feed mechanism 5 can be received.

(1-5-1-3) Belt Pressing Mechanism 90

As shown in FIG. 8, FIG. 9, and FIG. 12, the belt pressing mechanism 90of the second unit 62 is mainly configured from a twenty-fifth solenoid62 e (a fifteenth solenoid 61 e in the first unit 61) and a pressingmember 221 e. The pressing member 221 e is a member that can swing aboutthe support shaft 62 f, and the distal end section thereof is positionedbetween the upper-side belt and the lower-side belt of the upper belt221. Additionally, when the twenty-fifth solenoid 62 e is not beingdriven, the distal end section of the pressing member 221 e pressesdownward the lower-side belt of the upper belt 221 a using the force ofa spring member not shown in the drawings. That is, when thetwenty-fifth solenoid 62 e is not energized, the lower-side belt of theupper belt 221 is pressed toward the lower belt 222 by the distal endsection of the pressing member 221 e (see the solid lines in FIG. 10).When the twenty-fifth solenoid 62 e becomes driven by the control device9, the distal end section of the pressing member 221 e moves upward andthe pressing on the lower-side belt of the upper belt 221 is cancelled(see FIG. 9). In this state in which the pressing is cancelled, the beltpressing mechanism 90 no longer applies force to the upper belt 221.

It will be noted that when the lower-side belt of the upper belt 221 isreceiving the downward force by the belt pressing mechanism 90, as shownin FIG. 10, a gap dimension G2 between the lower-side belt of the upperbelt 221 and the upper-side belt of the lower belt 222 in theneighbourhood of the receiving unit 230 becomes relatively smaller. Whenthe force resulting from the belt pressing mechanism 90 is not acting onthe upper belt 221, as shown in FIG. 9, a gap dimension G1 between thelower-side belt of the upper belt 221 and the upper-side belt of thelower belt 222 in the neighbourhood of the receiving unit 230 becomesrelatively larger. The gap dimension G2 in FIG. 10 is smaller than thegap dimension G1 in FIG. 9. Consequently, in the state shown in FIG. 9in which the force resulting from the belt pressing mechanism 90 is notacting on the upper belt 221, the film F sandwiched between the upperbelt 221 and the lower belt 222 is not subjected to much restraint byboth belts 221 and 222. However, when the force resulting from the beltpressing mechanism 90 acts on the upper belt 221, as shown in FIG. 10,the vertical gap dimension G2 between both belts 221 and 222 becomessmaller and the degree to which the film F sandwiched between both belts221 and 222 is in close contact with both belts 221 and 222 becomeshigher.

(1-5-2) Clamp Device 23

As shown in FIG. 11, the clamp device 23 is disposed on the inner sideof the units 61 and 62 in the width direction of the film F (thefront-rear direction). The clamp device 23 has a front surface-sideclamp mechanism 23 b disposed in the neighbourhood of the first unit 61and a back surface-side clamp mechanism 23 c disposed in theneighbourhood of the second unit 62.

The front surface-side clamp mechanism 23 b and the back surface-sideclamp mechanism 23 c each have a first side clamp member 250, a centralclamp member 251, and a second side clamp member 252. The first sideclamp member 250, the central clamp member 251, and the second sideclamp member 252 are arranged side by side on a straight line as seen ina plan view.

The front surface-side clamp mechanism 23 b and the back surface-sideclamp mechanism 23 c extend in the right-left direction and clamp bothwidth direction side end portions of the film F. Resin strips 23 a forsandwiching the film F together with the clamp members 250, 251, and 252are disposed under the clamp members 250, 251, and 252.

Furthermore, the strips 23 a also extend in the right-left direction andhave substantially the same length as the combined longitudinaldirection length of the clamp members 250, 251, and 252. Thus, the clampmembers 250, 251, and 252, together with the strips 23 a, have the roleof a holding component that clamps the film F. The strips 23 a arelocated in positions in which the height positions of their uppersurfaces are slightly lower than the height positions of the uppersurfaces of the belts on the upper sides of the lower belts 222.

As shown in FIG. 12, the clamp device 23 is activated by solenoidsprovided in correspondence to the clamp members 250, 251, and 252.Specifically, in the front surface-side clamp mechanism 23 b, the firstside clamp member 250 is activated by a twelfth solenoid 61 b, thecentral clamp member 251 is activated by a thirteenth solenoid 61 c, andthe second side clamp member 252 is activated by a fourteenth solenoid61 d. In the back surface-side clamp mechanism 23 c, the first sideclamp member 250 is activated by a twenty-second solenoid 62 b, thecentral clamp member 251 is activated by a twenty-third solenoid 62 c,and the second side clamp member 252 is activated by a twenty-fourthsolenoid 62 d.

When the solenoids 61 b, 61 c, 61 d, 62 b, 62 c, and 62 d are activated,the six clamp members 250, 251, and 252 of the clamp device 23 arepressed down and apply downward loads to the strips 23 a. Thus, byactivating the solenoids 61 b, 61 c, 61 d, 62 b, 62 c, and 62 d whenthere is film F between the clamp members 250, 251, and 252 and thestrips 23 a, the film F is held in close contact between the clampmembers 250, 251, and 252 and the strips 23 a. By cancelling theactivation of the solenoids 61 b, 61 c, 61 d, 62 b, 62 c, and 62 d, theholding of the film F is cancelled.

It will be noted that, as shown in FIG. 11, the area in which the firstside clamp members 250, the central clamp members 251, and the secondside clamp members 252 contact the film F is large. In contrast, thearea in which the pressing members 221 e of the belt pressing mechanisms90 contact the upper belts 221 is small.

Furthermore, as shown in FIG. 2 and FIG. 4, a cutter mechanism 69 isprovided on the upstream side, in the film conveyance direction, of thefilm conveyance and holding mechanism 6. After the film F handed overfrom the film feed mechanism 5 to the film conveyance and holdingmechanism 6 is conveyed a predetermined amount, the cutter mechanism 69cuts the film F between both mechanisms 5 and 6. The cutter mechanism 69has a cutting blade that is longer than the width of the film, and thefilm F is cut as a result of the cutting blade being moved by anactuator.

(1-6) Sealing Mechanism 8

The sealing mechanism 8 heats and seals the bottom surface of the tray Tpushed out by the discharge pusher 75. It will be noted that, at thistime, the hold-down mechanism 81 also fulfills the role of pressing thetray T containing the product G against the upper surface of the sealingmechanism 8.

(1-7) Discharge Table 11

The discharge table 11 for discharging the completely wrapped tray Tcontaining the product G is provided on the front surface side of thesealing mechanism 8. A label issuer 16 affixes a label printed by alabel printer 15 to the tray T that has finished being wrapped.

(1-8) Control Device 9

The control device 9 is configured from a CPU, a RAM, a ROM, and thelike, controls the motors and solenoids shown in FIG. 12, and causes theconveyance and the wrapping of the film F to be carried out.

The operation of the stretch wrapping machine 1 carried out by thecontrol device 9 will be described below.

(2) Operation of Stretch Wrapping Machine 1

FIG. 13 to FIG. 17 are explanatory drawings for describing the operationof the stretch wrapping machine 1 carried out by the control device 9.

(2-1) General Operation of Stretch Wrapping Machine 1

First, as shown in FIG. 13, when the operator places the tray Tcontaining the product G on the weigh scale of the loading mechanism 2,the weigh scale waits for the weigh value to become stable and for theweighing to finish, and then the infeed conveyor belts start to move. Asthe infeed conveyor belts move, the projections secured to the infeedconveyor belts move from the front surface side to the back surfaceside. Because of this, the product G placed on the weigh scale is pushedout onto the support members 33 of the lifter mechanism 30 (see FIG.14).

Meanwhile, the film F that has been handed over by the film feedmechanism 5 from the film roll R to the film conveyance and holdingmechanism 6 is carried to over the lifter mechanism 30 by the conveyancedevices 22 of the first unit 61 and the second unit 62. Then, over thelifter mechanism 30, both width direction end portions of the film Fbecome held by activation of the clamp members 250 to 252.

Then, the ball screw mechanism 34 pushes the product G and the tray Tresting on the lifter mechanism 30 against the film F held by the clampmembers 250 to 252 (see FIG. 15). Because of this, the film F held bythe clamp members 250 to 252 stretches so as to cover the upper portionof the product G and the tray T.

In this state, when the rear tucking plate 78 and the right and lefttucking plates 76 and 77 move horizontally under the tray T, the fiveclamp members other than the central clamp member 251 of the frontsurface-side clamp mechanism 23 b cancel their holding of the film F atan appropriate timing, and three peripheral sides of the film F becometucked under the tray T (see FIG. 15). Then, when the discharge pusher75 pushes out the tray T toward the sealing mechanism 8, the one side ofthe film F on the front surface side that was not tucked hits the fronttucking rod 79 and becomes tucked under the tray T as the tray T movestoward the sealing mechanism 8. It will be noted that the central clampmember 251 of the front surface-side clamp mechanism 23 b at this timecancels its holding of the film F. Furthermore, as the tray T moves, thefilm F tucked under the tray T is heat-sealed by heat rollers of thesealing mechanism 8 (see FIG. 16), and when the tray T is discharged tothe position shown in FIG. 17 (when the tray T is discharged to thedischarge table 11), the wrapping is finished and the film F entirelycovers the product G and the tray T.

Moreover, the price, weight, and so forth of the product that have beencalculated on the basis of the weighed value in the control device 9 areprinted on a label by the label printer 15. Then, the label is affixedby the label issuer 16 to the tray T that has finished being wrapped.

(2-2) Conveyance of Film F

Next, the conveyance of the film F, and the holding of the film afterthe conveyance, by the film conveyance and holding mechanism 6 will bedescribed with reference to FIG. 18.

At the stage before the film insertion plate unit 51 that holds thedistal end of the film F approaches by horizontal movement, thereceiving units 230 of the film conveyance and holding mechanism 6 arein the second posture in which activation of the eleventh solenoid 61 aand the twenty-first solenoid 62 a is cancelled. That is, the distal endportions of the receiving units 230 are pushed up using the shaftmembers 231 a as spindles, so that the gripping components of the upperbelts 221 are out of contact with the film.

In this state, when the film insertion plate unit 51 approaches byhorizontal movement, the eleventh solenoid 61 a and the twenty-firstsolenoid 62 a are driven so that the gripping components of the upperbelts 221 come into contact with the film (step S1). Next, the drivingof the fifteenth solenoid 61 e and the twenty-fifth solenoid 62 e of thebelt pressing mechanisms 90 is cancelled, so that the pressing members221 e of the belt pressing mechanisms 90 press down the lower-side beltsof the upper belts 221 using the force of the spring members (step S2).This is the state shown in FIG. 10, in which the gap dimension G2between the lower-side belts of the upper belts 221 and the upper-sidebelts of the lower belts 222 in the neighborhoods of the receiving units230 becomes relatively smaller.

Next, the drive motor 65 a of the conveyance drive unit 65 is activatedto rotate the endless upper belts 221 and lower belts 222 of the units61 and 62 and horizontally convey the film F to the upper portion of thewrapping station 3 (step S3). At this time, because the gap dimension G2between the lower-side belts of the upper belts 221 and the upper-sidebelts of the lower belts 222 is relatively small, conveyance becomescarried out in a state in which the film F is in suitably close contactwith both belts 221 and 222.

When the film F is conveyed a predetermined amount, the drive motor 65 aof the conveyance drive unit 65 stops and the conveyance of the film Fis finished (step S4). Next, the wrapping is carried out, but duringthis wrapping, in view of the fact that wrapping cannot be done well ifthe film F is being subjected to excessive restraint by the upper belts221 and the lower belts 222 for conveyance, the fifteenth solenoid 61 eand the twenty-fifth solenoid 62 e of the belt pressing mechanisms 90are driven when the conveyance is finished (step S5). Because of this,the distal end sections of the pressing members 221 e of the beltpressing mechanisms 90 move upward, the pressing on the lower-side beltsof the upper belts 221 is cancelled (see FIG. 9), and the belt pressingmechanisms 90 no longer apply force to the upper belts 221. That is,because of step S5, the degree with which the film F is restrained bythe upper belts 221 and the lower belts 222 becomes extremely small.

At the same timing as step S5, in preparation for the wrapping, the sixsolenoids consisting of the twelfth solenoid 61 b, the thirteenthsolenoid 61 c, the fourteenth solenoid 61 d, the twenty-second solenoid62 b, the twenty-third solenoid 62 c, and the twenty-fourth solenoid 62d provided in correspondence to the clamp members 250, 251, and 252 ofthe clamp device 23 are driven (step S6). The timing of step S6 may alsobe earlier than the timing of step S5.

After this, as described above, the product G and the tray T resting onthe lifter mechanism 30 are pushed up against the film F held by theclamp members 250 to 252, and the wrapping begins.

(2-3) Control of Forward and Rearward Movement of Units 61 and 62Corresponding to Film Width

Next, the deciding of the front-rear positions of the first unit 61 andthe second unit 62 of the film conveyance and holding mechanism 6 willbe described with reference to FIG. 19.

The control device 9 acquires information relating to the product G froman internal storage device or from the outside. This informationincludes information relating to the type and dimension of the film F tobe used for wrapping. In this control, the control device 9 acquires thewidth dimension of the film F to be used (step S11).

The control device 9 has built-in data of proper wrapping conditionscorresponding to the width dimension of the film F. The proper wrappingconditions include conditions relating to the positions at which thefilm F should be held by the upper belts 221 and the lower belts 222during conveyance of the film F. Specifically, first distances andsecond distances are set with respect to several prescribed widthdimensions of the film F. The first distances are a distance WS1 a and adistance WS1 b shown in FIG. 20, and are front-rear distances betweenthe proper position in which the belts 221 and 222 of the first unit 61should hold the film F and the front surface-side end edge of the filmF. The second distances are a distance WS2 a and a distance WS2 b shownin FIG. 20, and are front-rear distances between the proper position inwhich the belts 221 and 222 of the second unit 62 should hold the film Fand the back surface-side end edge of the film F. In the example shownin FIG. 20, when the width dimension of the film F is FW1, the firstdistance is WS1 a and the second distance is WS2 a. Furthermore, whenthe width dimension of the film F is FW2 (FW2>FW1), the first distanceis WS1 b (WS1 b>WS1 a) and the second distance is WS2 b (WS2 b>WS2 a).That is, the control device 9 increases the first distance and thesecond distance when the width dimension of the film F increases.

The control device 9 decides the first distance and the second distanceon the basis of the data of the proper wrapping conditions correspondingto the width dimension of the film F (step S12).

Then, the control device 9 decides the front-rear position of the firstunit 61 corresponding to the first distance (step S13) and decides thefront-rear position of the second unit 62 corresponding to the seconddistance (step S14). Next, the control device 9 activates the drivemotors 63 a and 64 a of the unit moving devices 63 and 64 in order toset the units 61 and 62 in those front-rear positions (step S15).

It will be noted that the front-rear position of the first unit 61 isdecided in the range of the width of the cutouts 53 a in the two platemembers 57 a and 58 a (or the two plate members 57 b and 58 b). In aconventional stretch wrapping machine, the width of the cutouts 53 a isnarrow and the first unit 61 has practically been unable to be movedforward and backward. However, in the stretch wrapping machine 1pertaining to the present embodiment, the width dimension of the cutouts53 a is made larger than the width dimension of the other cutouts 53 bto 53 h, and the first unit 61 can be shifted somewhat in the front-reardirection (the width direction of the film F). Because of this, it ispossible to set the first distance to WS la or WS2 a for example (seeFIG. 20).

(3) Characteristics of Stretch Wrapping Machine 1

(3-1)

The stretch wrapping machine 1 pertaining to the present embodiment isequipped with the conveyance devices 22 of the film conveyance andholding mechanism 6, the clamp device 23, the lifter mechanism 30 andthe tucking mechanism 7 that serve as a wrapping component, and thecontrol device 9. Furthermore, the conveyance devices 22 have the beltconveyance units 220, which include the upper belts 221 and the lowerbelts 222, and the belt pressing mechanisms 90. Additionally, thepressing members 221 e of the belt pressing mechanisms 90 apply force tothe upper belts 221 so that the force with which the upper belts 221 andthe lower belts 222 sandwich the film F increases. Additionally, thecontrol device 9 controls the belt pressing mechanisms 90 so that duringthe conveyance of the film F the force resulting from the belt pressingmechanisms 90 acts on the upper belts 221 and so that after theconveyance of the film F the force resulting from the belt pressingmechanisms 90 that had acted on the upper belts 221 is cancelled (seesteps S2 and S5 in FIG. 18).

Because the stretch wrapping machine 1 employs this configuration,during the conveyance of the film F the force from the belt pressingmechanisms 90 acts on one (the upper belts 221) of the upper belts 221and the lower belts 222 that sandwich the end portions of the film F.For this reason, the force with which both belts 221 and 222 sandwichthe film F becomes stronger. Because of this, the conveyance of the filmF is carried out stably. After the conveyance of the film F the forcethat had acted on the upper belts 221 from the belt pressing mechanisms90 is cancelled, so the conveyed film F is no longer excessivelyrestrained by both belts 221 and 222, and the wrapping with the film Fheld by the clamp devices 23 is also carried out excellently.

(3-2)

In the stretch wrapping machine 1 pertaining to the present embodiment,the force that had acted on the upper belts 221 from the belt pressingmechanisms 90 is cancelled prior to the wrapping, so the wrapping can bestarted in a state in which the film F is not being excessivelyrestrained by both belts 221 and 222. Because of this, the wrapping isstable.

(3-3)

The clamp devices 23 of the film conveyance and holding mechanism 6 ofthe stretch wrapping machine 1 pertaining to the present embodiment havethe six clamp members 250, 251, and 252 and the strips 23 a. The lowersurfaces of the clamp members 250, 251, and 252 are holding surfaces(first holding surfaces) that hold the film F. The upper surfaces of thestrips 23 a are holding surfaces (second holding surfaces) that hold thefilm F and oppose the lower surfaces of the clamp members 250, 251, and252. Additionally, the clamp members 250, 251, and 252 and the strips 23a hold the film F by sandwiching sections of the film F other than thesections of the film F positioned between the upper belts 221 and thelower belts 222. Specifically, the clamp members 250, 251, and 252 andthe strip 23 a of the front surface-side clamp mechanism 23 b hold thefilm F further on the back surface side than the upper belt 221 and thelower belt 222 of the first unit 61, and the clamp members 250, 251, and252 and the strip 23 a of the back surface-side clamp mechanism 23 chold the film F further on the front surface side than the upper belt221 and the lower belt 222 of the second unit 62 (see FIG. 11).

In the stretch wrapping machine 1 employing this configuration, thesections of the film F held by the clamp devices 23 are not the sectionsof the film F between the upper belts 221 and the lower belts 222 butare located in positions away from those sections. For this reason, thepositions of the sections of the film F held by the clamp devices 23 canbe set in positions suitable for the wrapping.

(3-4)

In the stretch wrapping machine 1 pertaining to the present embodiment,the areas in which the pressing members 221 e of the belt pressingmechanisms 90 contact the upper belts 221—that is, the areas of thepressing surfaces of the pressing members 221 e—are small

The areas in which the clamps 250, 251, and 252 contact the film F arelarger than the areas of the pressing surfaces of the pressing members221 e.

Because the stretch wrapping machine 1 employs this configuration, theclamp devices 23 can strongly hold the film F when pushing the tray Tand the product G against the film F during the wrapping.

Furthermore, during the conveyance of the film F, frictional resistancebetween the pressing surfaces of the pressing members 221 e and theupper belts 221 can be kept down because the areas of the pressingsurfaces of the pressing members 221 e of the belt pressing mechanisms90 are small Because of this, the movement of the upper belts 221becomes smooth, and in the stretch wrapping machine 1 the conveyance ofthe film F is stable.

(3-5)

The film conveyance and holding mechanism 6 of the stretch wrappingmachine 1 pertaining to the present embodiment is equipped with thefirst unit 61, which uses the upper belt 221 and the lower belt 222 tohold the front surface-side end portion of the film F and convey thefilm F, and the second unit 62, which uses the upper belt 221 and thelower belt 222 to hold the back surface-side end portion of the film Fand convey the film F. Moreover, in the film conveyance and holdingmechanism 6, the first unit 61 is configured to move in the widthdirection of the film F by activation of the first unit moving device 63and the second unit 62 is configured to move in the width direction ofthe film F by activation of the second unit moving device 64.Additionally, the control device 9 decides the first distance and thesecond distance on the basis of the data of the proper wrappingconditions corresponding to the width dimension of the film F (see stepS12 in FIG. 18) and causes the first unit 61 and the second unit 62 tomove to positions corresponding to the first distance and the seconddistance.

In the stretch wrapping machine 1 employing this configuration, thedistances (the first distance and the second distance) from the endedges of the film F in the sections of the film F sandwiched by bothbelts 221 and 222 of each unit 61 and 62 can be set to appropriatedistances in accordance with the width dimension of the film. Because ofthis, slackness in the film F during the conveyance of the film F isreduced and therefore the conveyance of the film F is stable.

Specifically, the control device 9 increases the first distance and alsoincreases the second distance when the width dimension of the film Fincreases (see FIG. 20). That is, in the stretch wrapping machine 1, thefirst distance and the second distance increase when the width dimensionof the film F increases, so each unit 61 and 62 conveys the film F whilesandwiching, with both belts 221 and 222, sections of the film Fpositioned more inward in the film width direction when the widthdimension of the film F is large than when it is small. Because of this,there is less sagging in the film width direction central section of thefilm F, and the conveyance of the film F is stable.

(4) Example Modifications

An embodiment of the present invention has been described above on thebasis of the drawings, but the specific configurations are not limitedto the embodiment and can be changed to the extent that they do notdepart from the spirit of the invention.

(4-1) Example Modification A

In the embodiment, the force resulting from the belt pressing mechanisms90 acts on the upper belts 221, but it is also possible to employ beltpressing mechanisms that press the lower belts 222 up toward the upperbelts 221.

(4-2) Example Modification B

In the embodiment, the belt pressing mechanism 90 of each unit 61 and 62uses one pressing member 221 e to press the upper belt 221, but it isalso possible to employ a belt pressing mechanism having plural pressingmembers. In a case where pressing members are provided in several placesalong the conveyance direction of the film F, the film holding forceduring the conveyance by the pair of upper and lower belts can beincreased.

(4-3) Example Modification C

To the stretch wrapping machine 1 of the embodiment may also be added ablower device 300 that further improves the stability of the conveyanceof the film F. As shown in FIG. 21, it is preferred that the blowerdevice 300 be disposed in the section where conveyance is started by thefilm conveyance and holding mechanism 6—that is, in the space above thereceiving units 230—and gently blow air toward the leading end of thefilm when conveyance starts. When the downward air flow indicated byarrow A2 in FIG. 21 hits the leading end of the film F when conveyancestarts, the leading end of the film F faces a little downward duringconveyance, and the leading end of the film F is kept from curling upwhile the film F is conveyed.

In this way, the phenomenon of up-floating of the leading end of thefilm F upward during conveyance is controlled, so that there no longerarise troubles such as the leading end of the film F getting caught onthe right and left tucking plates 76 and 77 of the tucking mechanism 7.

It will be noted that although it is also conceivable to use a metalguide member to prevent up-floating of the leading end of the film Fupward during conveyance, in that case contact between the film F andthe guide member impairs the stability of the conveyance of the film Fand ends up creating resistance. With the stretch wrapping machinepertaining to example modification C, the stability of the conveyance ofthe film is virtually not impaired.

REFERENCE SIGNS LIST

-   1 Stretch Wrapping machine-   3 Wrapping Station (Wrapping Component)-   7 Tucking Mechanism (Wrapping Component)-   9 Control Device (Control Component)-   22 Conveyance Device (Conveyance Component) of Film Conveyance and    Holding Mechanism-   23 Clamp Device (Holding Component) of Film Conveyance and Holding    Mechanism-   23 a Strip (Second Holding Member of Holding Component)-   30 Lifter Mechanism (Wrapping Component)-   61 e Fifteenth Solenoid (Drive Component of Force Applying    Component)-   62 e Twenty-Fifth Solenoid (Drive Component of Force Applying    Component)-   90 Belt Pressing Mechanism 90 (Force Applying Component)-   61 First Unit (First Conveyance Unit) of Film Conveyance and Holding    Mechanism-   62 Second Unit (Second Conveyance Unit) of Film Conveyance and    Holding Mechanism-   63 First Unit Moving Device (First Unit Moving Component)-   64 Second Unit Moving Device (Second Unit Moving Component)-   220 Belt Conveyance Unit (First Conveyance Unit; Second Conveyance    Unit)-   221 Upper Belt (First Belt; Third Belt)-   221 e Pressing Member (Pressing Member of Force Applying Component)-   222 Lower Belt (Second Belt; Fourth Belt)-   250 First Side Clamp Member (First Holding Member of Holding    Component)-   251 Central Clamp Member (First Holding Member of Holding Component)-   252 Second Side Clamp Member (First Holding Member of Holding    Component)-   F Film-   FW1 Width Dimension of Film-   FW2 Width Dimension of Film-   G Product (Wrapping Item)-   T Tray (Wrapping Item)-   WS1 a, WS1 b First Distances-   WS2 a, WS2 b Second Distances

CITATION LIST Patent Literature

Patent Document 1: JP-A No. 2006-327670

1. A stretch wrapping machine comprising: a conveyance component thatconveys film pulled out from a film roll; a holding component that holdsthe film conveyed by the conveyance component; a wrapping component thatpushes a wrapping item against the film held by the holding componentand uses the film to wrap the wrapping item; and a control componentthat controls the operations of the conveyance component, the holdingcomponent, and the wrapping component, wherein the conveyance componenthas a first conveyance unit including a first belt and a second beltthat sandwich an end portion of the film and a force applying componentthat applies force to the first belt so that the force with which thefirst belt and the second belt sandwich the film increases, and thecontrol component controls the force applying component so that duringthe conveyance of the film by the conveyance component the forceresulting from the force applying component acts on the first belt andso that after the conveyance of the film by the conveyance component theforce resulting from the force applying component that had acted on thefirst belt is cancelled.
 2. The stretch wrapping machine according toclaim 1, wherein after the conveyance of the film by the conveyancecomponent the control component has the holding component hold the filmand causes the wrapping by the wrapping component to be carried out in astate in which the force resulting from the force applying componentthat had acted on the first belt is cancelled.
 3. The stretch wrappingmachine according to claim 1, wherein the holding component has a firstholding member in which a first holding surface is formed and a secondholding member in which a second holding surface that opposes the firstholding surface is formed, and the first holding member and the secondholding member hold the film by sandwiching a section of the film otherthan the section of the film positioned between the first belt and thesecond belt.
 4. The stretch wrapping machine according to claim 3,wherein the force applying component has a pressing member in which apressing surface that presses the first belt is formed and a drivecomponent that moves the pressing member, and the area of the pressingsurface of the pressing member is smaller than that of the first holdingsurface of the first holding member.
 5. The stretch wrapping machineaccording to claim 1, wherein the first conveyance unit uses the firstbelt and the second belt to sandwich the end portion which is one endportion of the film and convey the film, the conveyance componentfurther has a second conveyance unit that uses a third belt and a fourthbelt to sandwich another end portion of the film and convey the film,the stretch wrapping machine further comprises a first unit movingcomponent that causes the first conveyance unit to move in a film widthdirection intersecting a conveyance direction of the film and a secondunit moving component that causes the second conveyance unit to move inthe film width direction, and in accordance with the width dimension ofthe film the control component controls the first unit moving componentto change a first distance which is a distance from one end edge of thefilm in the one end portion of the film sandwiched by the first belt andthe second belt of the first conveyance unit and controls the secondunit moving component to change a second distance which is a distancefrom another end edge of the film in the other end portion of the filmsandwiched by the third belt and the fourth belt of the secondconveyance unit.
 6. The stretch wrapping machine according to claim 5,wherein the control component increases the first distance and increasesthe second distance when the width dimension of the film increases.